STUDIES IN MEMORY. — часть 1

RECALL OF WORDS, OBJECTS AND MOVEMENTS.

BY HARVEY A. PETERSON.

Kirkpatrick,1 in experimenting with 379 school children and college students, found that 3-1/3 times as many objects were recalled as visual words after an interval of three days. The experiment consisted in showing successively 10 written names of common objects in the one case and 10 objects in the other at the rate of one every two seconds. Three days later the persons were asked to recall as many of each series as possible, putting all of one series together. The averages thus obtained were 1.89 words, 6.29 objects. The children were not more dependent on the objects than the college students.

Since the experiment just described was performed without laboratory facilities, Calkins2 repeated it with 50 college women, substituting lantern pictures for objects. She obtained in recall, after two days, the averages 4.82 words, 7.45 pictures. The figures, however, are the number of objects or words remembered out of ten, not necessarily correctly placed. Kirkpatrick's corresponding figures for college women were 3.22 words, 5.44 objects. The two experiments substantially agree, Calkins' higher averages being probably due to the shortening of the interval to two days.

Assuming, thus, that objects are better remembered than names in deferred recall, the question arises whether this holds true when the objects and names are coupled with strange and arbitrary symbols—a question which is clearly of great practical interest from the educational point of view, as it is involved in the pedagogical problem whether a person seeking to acquire the vocabulary of a foreign language ought to connect the foreign words with the familiar words or with the objects themselves. And the further question arises: what are the facts in the case of movements instead of objects, and correspondingly in that of verbs instead of nouns. Both questions are the problems of the following investigation.

As foreign symbols, either the two-figure numbers were used or nonsense-words of regularly varying length. As familiar material, nouns, objects, verbs and movements were used. The words were always concrete, not abstract, by which it is meant that their meaning was capable of demonstration to the senses. With the exception of a few later specified series they were monosyllabic words. The nouns might denote objects of any size perceptible to the eye; the objects, however, were all of such a size that they could be shown through a 14×12 cm. aperture and still leave a margin. Their size was therefore limited.

Concerning the verbs and movements it is evident that, while still being concrete, they might be simple or complicated activities consuming little or much time, and further, might be movements of parts of the body merely, or movements employing other objects as well. In this experiment complicated activities were avoided even in the verb series. Simple activities which could be easily and quickly imaged or made were better for the purpose in view.

THE A SET.

The A set contained sixteen series, A¹, A², A³, etc., to A¹⁶. They were divided as follows:

Numbers and nouns: A¹, A⁵, A⁹, A¹³.

Numbers and objects: A², A⁶, A¹⁰, A¹⁴.

Numbers and verbs: A³, A⁷, A¹¹, A¹⁵.

Numbers and movements: A⁴, A⁸, A¹², A¹⁶.

The first week A^1-4 were given, the second week A^5-8, etc., so that each week one series of each of the four types was given the subject.

In place of foreign symbols the numbers from 1 to 99 were used, except in A^13-15, in which three-figure numbers were used.

Each series contained seven couplets, except A^13-16, which, on account of the greater difficulty of three-figure numbers, contained five. Each couplet was composed of a number and a noun, object, verb, or movement.

Certain rules were observed in the composition of the series. Since the test was for permanence, to avoid confusion no number was used in more than one couplet. No two numbers of a given series were chosen from the same decade or contained identical final figures. No word was used in more than one couplet. Their vowels, and initial and final consonants were so varied within a single series as to eliminate phonetic aids, viz., alliteration, rhyme, and assonance. The kind of assonance avoided was identity of final sounded consonants in successive words, e.g., lane, vine.

The series were composed in the following manner: After the twenty-eight numbers for four series had been chosen, the words which entered a given series were selected one from each of a number of lists of words. These lists were words of like-sounded vowels. After one word had been chosen from each list, another was taken from the first list, etc. As a consequence of observing the rules by which alliteration, rhyme, and assonance were eliminated, the words of a series usually represented unlike categories of thought, but where two words naturally tended to suggest each other one of them was rejected and the next eligible word in the same column was chosen. The following is a typical series from the A set.

The apparatus used in the A set and also in all the later sets may be described as follows: Across the length of a table ran a large, black cardboard screen in the center of which was an oblong aperture 14 cm. high and 12 cm. wide. The center of the aperture was on a level with the eyes of the subject, who sat at the table. The aperture was opened and closed by a pneumatic shutter fastened to the back of the screen. This shutter consisted of two doors of black cardboard sliding to either side. By means of a large bulb the length of exposure could be regulated by the operator, who stood behind the table.

The series—consisting of cards 4×2½ cm., each containing a printed couplet—was carried on a car which moved on a track behind and slightly below the aperture. The car was a horizontal board 150 cm. long and 15 cm. wide, fixed on two four-wheeled trucks. It was divided by vertical partitions of black cardboard into ten compartments, each slightly wider than the aperture to correspond with the visual angle. A curtain fastened to the back of the car afforded a black background to the compartments. The couplets were supported by being inserted into a groove running the length of the car, 3 cm. from the front. A shutter 2 cm. high also running the length of the car in front of the groove, fastened by hinges whose free arms were extensible, concealed either the upper or the lower halves of the cards at the will of the operator; i.e., either the foreign symbols or the words, respectively. A screen 15 cm. high and the same length as the car, sliding in vertical grooves just behind the cards and in front of the vertical partitions, shut off the objects when desired, leaving only the cards in view. Thus the apparatus could be used for all four types of series.

The method of presentation and the time conditions of the A set were as follows:—A metronome beating seconds was used. It was kept in a sound-proof box and its loudness was therefore under control. It was just clearly audible to both operator and subject. In learning, each couplet was exposed 3 secs., during about 2 secs. of which the shutter was fully open and motionless. During this time the subject read the couplet inaudibly as often as he wished, but usually in time with the metronome. His object was to associate the terms of the couplet. There was an interval of 2 secs. after the exposure of each couplet, and this was required to be filled with repetition of only the immediately preceding couplet. After the series had been presented once there was an interval of 2 secs. additional, then a second presentation of it commenced and after that a third. At the completion of the third presentation there was an interval of 6 secs. additional instead of the 2, at the expiration of which the test commenced.

A^13-16 had five presentations instead of three. The test consisted in showing the subject either the numbers or the words in altered order and requiring him to write as many of the absent terms as he could. In the object and movement series the objects were also shown and the movements repeated by the subject if words were the given terms. The time conditions in the test were,

This allowed the subject 7 secs. for recalling and writing each term in A^1-12 and 9 sec. in A^13-16. If a word was recalled after that time it was inserted, but no further insertions were made after the test of a series had been completed. An interval of 3 min. elapsed between the end of the test of one series and the beginning of the next series, during which the subject recorded the English word of any couplet in which an indirect association had occurred, and also his success in obtaining visual images if the series was a noun or a verb series.

As already indicated, four series—a noun, an object, a verb, and a movement series—given within a half hour, constituted a day's work throughout the year. Thus variations due to changes in the physiological condition of the subject had to affect all four types of series.

Two days later these series were tested for permanence, and in the same way as the tests for immediate recall, with this exception:

Thus 11 secs. were allowed for the deferred recall of each term in A^13-16.

In the movement series of this set, to avoid hesitation and confusion, the operator demonstrated to the subject immediately before the series began, once for each word, how the movements were to be made.

The A set was given to three subjects. The results of each subject are arranged separately in the following table. In the tests the words were required in A^1-4, in A^5-16 the numbers. The figures show the number of terms correctly recalled out of seven couplets in A^1-12 and out of five couplets in A^13-16, exclusive of indirect association couplets. The figures in brackets indicate the number of correctly recalled couplets per series in which indirect associations occurred. The total number correctly recalled in any series is their sum. The figures in the per cent. row give the percentage of correctly recalled couplets left after discarding both from the number recalled and from the total number of couplets given those in which indirect associations occurred. This simply diminished the subject's number of chances. A discussion of the propriety of this elimination will be found later. In A^1-12 the absent terms had to be recalled exactly in order, to be correct, but in A^13-16, on account of the greater difficulty of the three-place numbers, any were considered correct when two of the three figures were recalled, or when all three figures were correct but two were reversed in position, e.g., 532 instead of 523. N means noun series, O object, V verb, and M movement series. Series A¹, A⁵, A⁹, A¹³ are to be found in the first and third columns, A², A⁶, A¹⁰, A¹⁴ in the second and fourth, A³, A⁷, A¹¹, A¹⁵, in the fifth and seventh, and A⁴, A⁸, A¹², A¹⁶ in the sixth and eighth columns.

TABLE I.

SHOWING IMMEDIATE RECALL AND RECALL AFTER TWO DAYS.

These results will be included in the discussion of the results of the B set.

THE B SET.

A new material was needed for foreign symbols. After considerable experimentation nonsense words were found to be the best adapted for our purpose. The reasons for this are their regularly varying length and their comparative freedom from indirect associations. An objection to using nonsense syllables in any work dealing with the permanence of memory is their sameness. On this account they are not remembered long. To secure a longer retention of the material, nonsense words were devised in substantially the same manner as that in which Müller and Schumann made nonsense syllables, except that these varied regularly in length from four to six letters. Thus the number of letters, not the number of syllables was the criterion of variation, though of course irregular variation in the number of syllables was a necessary consequence.

When the nonsense words were used it was found that far fewer indirect associations occurred than with nonsense syllables. By indirect association I mean the association of a foreign symbol and its word by means of a third term suggested to the subject by either of the others and connected at least in his experience with both. Usually this third term is a word phonetically similar to the foreign symbol and ideationally suggestive of the word to be associated. It is a very common form of mnemonic in language material. The following are examples:

cax, stone (Caxton);
teg, bib (get bib);
laj, girl (large girl);
xug, pond (noise heard from a pond);
gan, mud (gander mud).

For both of these reasons nonsense words were the material used as foreign symbols in the B set.

The nonsense words were composed in the following manner. From a box containing four of each of the vowels and two of each of the consonants the letters were chosen by chance for a four-letter, a five-letter, and a six-letter word in turn. The letters were then returned to the box, mixed, and three more words were composed. At the completion of a set of twelve any which were not readily pronounceable or were words or noticeably suggested words were rejected and others composed in their places.

The series of the B set were four couplets long. Each series contained one three-letter, one four-letter, one five-letter, and one six-letter nonsense word. The position in the series occupied by each kind was constantly varied. In all other respects the same principles were followed in constructing the B set as were observed in the A set with the following substitutions:

No two foreign symbols of a series and no two terms of a couplet contained the same sounded vowel in accented syllables.

The rule for the avoidance of alliteration, rhyme, and assonance was extended to the foreign symbols, and to the two terms of a couplet.

The English pronounciation was used in the nonsense words. The subjects were not informed what the nonsense words were. They were called foreign words.

Free body movements were used in the movement series as in the A set. Rarely an object was involved, e.g., the table on which the subject wrote. The movements were demonstrated to the subject in advance of learning, as in the A set.

The following are typical B series:

The time conditions for presenting a series remained practically the same. In learning, the series was shown three times as before. The interval between learning and testing was shortened to 4 seconds, and in the test the post-term interval of A^13-16 retained (6 secs.). This allowed the subject 9 secs. for recalling and writing each term. The only important change was an extension of the number of tests from two to four. The third test was one week after the second, and the fourth one week after the third. In these tests the familiar word was always the term required, as in A^1-4, on account of the difficulty of dealing statistically with the nonsense words. The intervals for testing permanence in the B set may be most easily understood by giving the time record of one subject.

The two half-hours in a week during which all the work of one subject was done fell on approximately the same part of the day. When a number of groups of 4 series each were to be tested on a given day they were taken in the order of their recency of learning. Thus on March 7 the order for Hu was B^13-16, B^9-12, B^5-8.

Henceforth there was also rotation within a given four series. As there were always sixteen series in a set, the effects of practice and fatigue within a given half-hour were thus eliminated.

In the following table the results of the B set are given. Its arrangement is the same as in Table 1., except that the figures indicate the number of absent terms correctly recalled out of four couplets instead of seven or five. Where blanks occur, the series was discontinued on account of lack of recall. As in Table 1., the tables in the first, third and fifth columns show successive stages of the same series. Immediate recall is omitted because with rare exceptions it was perfect, the test being given merely as an aid in learning.

TABLE II.

SHOWING RECALL AFTER TWO, NINE, AND SIXTEEN DAYS.

¹Four presentations in learning.
²Five presentations in learning.
³Five days' interval instead of two.

In the following summary the recall after two days is combined from Tables I. and II. for the three subjects M, S and Hu, there being no important difference in the conditions of experimentation. For the three other subjects this summary is merely a résumé of Table II. The recall after nine and sixteen days in Table II. is omitted, and will be taken up later. The figures are in all cases based on the remainders left after those couplets in which indirect associations occurred were eliminated both from the total number of couplets learned and from the total number correctly recalled. E.g., in the case of nouns, M learned, in all, 42 couplets in the A and B sets, but since in 3 of them indirect associations occurred, only 39 couplets are left, of which 21 were correctly recalled. This gives 54 per cent.

SUMMARY OF RECALL AFTER TWO DAYS.—FROM TABLES I. AND II.

Av. gain in object couplets, 19 per cent. Av. gain in movement couplets, 30 per cent.

The first question which occurs in examining the foregoing tables is concerning the method of treating the indirect associations, i.e., obtaining the per cents. The number of couplets correctly recalled may be divided into two classes: those in which indirect associations did not occur, and those in which they did occur. Those in which they did not occur furnish us exactly what we want, for they are results which are entirely free from indirect associations. In them, therefore, a comparison can be made between series using objects and activities and others using images. On the other hand, those correctly recalled couplets in which indirect associations did occur are not for our purposes pure material, for they contain not only the object-image factor but the indirect association factor also. The solution is to eliminate these latter couplets, i.e., subtract them both from the number correctly recalled and from the total number of couplets in the set for a given subject. By so doing and by dividing the first remainder by the second the per cents, in the tables were obtained. There is one exception to this treatment. The few couplets in which indirect associations occurred but which were nevertheless incorrectly recalled are subtracted only from the total number of couplets in the set.

The method by which the occurrence of indirect associations was recorded has been already described. It is considered entirely trustworthy. There is usually little doubt in the mind of a subject who comprehends what is meant by an indirect association whether or not such were present in the particular series which has just been learned. If none occurred in it the subjects always recorded the fact. That an indirect association should occasionally be present on one day and absent on a subsequent one is not strange. That a second term should effect a union between a first and third and thereafter disappear from consciousness is not an uncommon phenomenon of association. There were thirteen such cases out of sixty-eight indirect associations in the A, B and C sets. In the tables they are given as present because their effects are present. When the reverse was the case, namely, when an indirect association occurred on the second, ninth or sixteenth day for the first time, it aided in later recall and was counted thereafter. There were eight such cases among the sixty-eight indirect associations.

Is it possible that the occurrence of indirect associations in, e.g., two of the four couplets of a series renders the retention of the other two easier? This could only be so when the intervals between two couplets in learning were used for review, but such was never the case. The subjects were required to fill such intervals with repetitions of the preceding couplet only.

The elimination of the indirect association couplets and the acceptance of the remainders as fair portrayals of the influence of objects and movements on recall is therefore a much nearer approach to truth than would be the retention of the indirectly associated couplets.

The following conclusions deal with recall after two days only. The recall after longer intervals will be discussed after Table III.

The summary from Tables I. and II. shows that when objects and nouns are coupled each with a foreign symbol, four of the six subjects recall real objects better than images of objects, while two, M and Ho, show little or no preference. The summary also shows that when body movements and verbs are coupled each with a foreign symbol, five of the six subjects recall actual movements better than images of movements, while one subject, M, shows no preference. The same subject also showed no preference for objects. With the subjects S and B the preference for actual movements is not marked, and has importance only in the light of later experiments to be reported.

The great difference in the retentive power of different subjects is, as we should expect, very evident. Roughly, they may be divided into two groups. M and Mo recall much more than the other four. The small percentage of recall in the case of these four suggested the next change in the conditions of experimentation, namely, to shorten with them the intervals between the tests for permanence. This was accordingly done in the C set. But before giving an account of the next set we may supplement these results by results obtained from other subjects.

It was impossible to repeat this set with the same subjects, and inconvenient, on account of the scarcity of suitable words, to devise another set just like it. Accordingly, the B set was repeated with six new subjects. We may interpolate the results here, and then resume our experiments with the other subjects. The conditions remained the same as for the other subjects in all respects except the following. The tests after nine and sixteen days were omitted, and the remaining test for deferred recall was given after one day instead of after two. In learning the series, each series was shown four times instead of three. The results are summarized in the following table. The figures in the left half show the number of words out of sixteen which were correctly recalled. The figures in parentheses separate, as before, the correctly recalled indirect-association couplets. In the right half of the table the same results, omitting indirect-association couplets, are given in per cents, to facilitate comparison with the summary from Tables I. and II.

TABLE III.

SHOWING RECALL AFTER ONE DAY.

Av. gain in object couplets, 30 per cent. Av. gain in movement couplets, 12 per cent.

The table shows that five subjects recall objects better than images of objects, while one subject recalls images of objects better. Similarly, three subjects recall actual movements of the body better than images of the same, while with three neither type has any advantage.

THE C SET.

In the C set certain conditions were different from the conditions of the A and B sets. These changes will be described under three heads: changes in the material; changes in the time conditions; and changes in the method of presentation.

For lack of monosyllabic English words the verbs and movements were dissyllabic words. The nouns and objects were monosyllabic, as before. All were still concrete, and the movements, whether made or imaged, were still simple. But the movements employed objects, instead of being merely movements of the body.

For two of the subjects, M and Mo, the time intervals between the tests remained as in the A and the B sets, namely, two days, nine days, and sixteen days. With the four other subjects, S, Hu, B and Ho, the number of tests was reduced to three and the intervals were as follows:

The I. test, which as before was a part of the learning process, was not counted. The II. test followed from 4½ to 6½ hours, or an average of 5-3/8 hours, after the I. test. The III. test was approximately 16 hours after the II. test for all four subjects.

The series were learned between 10 a.m. and 1:30 p.m., the II. test was the same day between 4:30 and 5:10 p.m., and the III. test was the following morning between 8:30 and 9:10 a.m. Each subject of course came at the same hour each week.

Each series was shown three times, as in the B set.

A change had to be made in the length of exposure of each couplet in the movement series. For, as a rule, movements employing objects required a longer time to execute than mere movements of the body. Five seconds was found to be a suitable length of exposure. To keep the three other types of series comparable with the movement series, if possible, their exposure was also increased from 3 to 5 secs. The interval of 2 secs, at the end of a presentation was omitted, and the interval between learning and testing reduced from 4 secs, in the B set to 2 secs.

In the movement series of the A and B sets, movements of parts of the body were chosen. But the number of such movements which a person can conveniently make while reading words shown through an aperture is limited, and as stated above no single word was ever used in two couplets. These were now exhausted. In the C set, therefore, movements employing objects were substituted. The objects lay on the table in a row in front of the subject, occupying a space about 50 cm. from left to right, and were covered by a black cambric cloth. They were thus all exposed at the same moment by the subject who, at a signal, laid back the cloth immediately before the series began, and in the same manner covered them at the end of the third presentation. Thus the objects were or might be all in view at once, and as a result the subject usually formed a single mental image of the four objects.

With this kind of material it was no longer necessary for the operator to show the subject in advance of the series what the movements were in order to avoid hesitation and confusion, for the objects were of such a nature as obviously to suggest in connection with the words the proper movements.

TABLE IV.

SHOWING RECALL AFTER TWO, NINE AND SIXTEEN DAYS FOR TWO SUBJECTS, AND AFTER FIVE HOURS AND TWENTY-ONE HOURS FOR FOUR OTHER SUBJECTS.

The object series were also changed to conform to the movement series. Formerly the objects had been shown successively through the aperture and synchronously with their corresponding words; now they were on the table in front of the subject and all uncovered and covered at once as in the movement series. The subjects therefore had a single mental image of these four objects also.

In both the object and the movement series the objects as before were small and fairly uniform in size and so selected as not to betray to the subject their presence beneath the cloth in the I. test. In the II., III. and IV. tests there were no objects on the table.

The previous table shows the results of the C set. The figures give the number of couplets correct out of four; the figures in brackets give the number of indirect associations; the total number recalled in any series is their sum.

In the following summary the recall of M and Mo after two days and of S, Hu, B and Ho after twenty-one hours are combined.

SUMMARY FROM TABLE IV.

Av. gain in object couplets, 22 per cent.
Av. gain in movement couplets, 36 per cent.

Before asking whether the results of the C set confirm the conclusions already reached, we must compare the conditions of the three sets to see whether the changes in the conditions in the C set have rendered it incomparable with the other two. The first change was the substitution of dissyllabic words in the verb and the movement series in the place of monosyllabic words. Since the change was made in both the verb and the movement series their comparability with each other is not interfered with, and this is the point at issue. Preliminary tests, however, made it highly probable that simple concrete dissyllabic words are not more difficult than monosyllabic in 5 secs. exposure. This change is therefore disregarded.

The first important change introduced in the C set was the reduction of the intervals between the tests for four subjects. The second was the lengthening of the exposure from 3 to 5 secs. These changes also do not lessen the comparability of the noun, object, verb and movement series with one another, since they affected all series of the C set.

The third change in the conditions was the substitution in the movement series of movements employing objects for movements of the body alone, and the consequent placing of objects on the table in the movement and in the object series of which the subject obtained a single mental image. All of the subjects were of the opinion that this single mental image was an aid in recall. Each of the objects contributing to form it was individualized by its spatial order among the objects on the table. The objects shown through the aperture were connected merely by temporal contiguity. On this account the object and the movement series of the C set are not altogether comparable with those of the A and the B sets. We should expect a priori that the object and the movement series in the C set would be much better recalled than those of the A and the B sets.

The fourth change was from imaged or made movements of the body alone to imaged or made movements employing objects. If, as the A and the B sets have already demonstrated, the presence of objects at all is an aid to recall, the movement series of the C set should show a greater gain over their corresponding verb series than the simple movements of the body in the A and the B sets showed over their corresponding verb series. For, employing objects in movements is adding the aid of objects to whatever aid there is in making the movements.

Turning to the results, we consider the C set by itself with reference to the effect of the use of objects vs. images in general. The summary from Table IV. shows that under the conditions given, after intervals of from slightly less than one day to two days, five of the six subjects recall object couplets better than noun couplets. One subject, M recalls noun couplets better. It also shows that under the conditions and after the intervals mentioned all six subjects recall movement couplets better than verb couplets. In view of the small difference here and of his whole record, however, M is probably to be classed as indifferent in both substantive and action series.

RECALL AFTER NINE AND SIXTEEN DAYS.

Thus far recall after these longer intervals has not been discussed. The experiment was originally devised to test recall after two days only, but it was found that with two of the subjects, M and Mo, recall for greater intervals could be obtained with slight additional trouble. This was accordingly done in the B and C sets. The results of the four other subjects in the B set are not so satisfactory on this point, because not enough was recalled.

The most interesting fact which developed was an apparently slower rate of forgetting, in many cases, of the nouns and verbs than of the objects and movements. In the noun-object group of the B set it is noticeable in three out of the four possible subjects, viz., B, Ho, and Mo. M alone does not show it. The two other subjects, S and B, did not recall enough for a comparison. In the verb-movement group of the B set it is also marked in three out of the four possible subjects, viz., M, Ho, and Mo. B alone does not show it. It is also seen in the C set in the results of M and Mo, in both the noun-object and the verb-movement groups. With the four other subjects in the C set it could not be noticed, since the series ran their course in a day. In M (verb-movement group, C set) and Mo (noun-object group, C set) the originally higher object or movement curves actually fall below their corresponding noun or verb curves.

The results of the tests for recall after nine and sixteen days are summarized in the following tables. They should be compared with the recall of these same series after two days given in Tables II. and IV., nor should it be forgotten that all four types started with perfect immediate recall. The figures give per cents, correct after eliminating indirect-association couplets.

TABLE V.

SHOWING RECALL AFTER NINE AND SIXTEEN DAYS.—SUMMARY FROM B SET.

TABLE VI.

SAME FOR M AND Mo.—SUMMARY FROM C SET.

THE D SET.

A few series of nouns, objects, verbs, and movements dissociated from foreign symbols were obtained. The material was of the same kind as the words used in the couplet series, being mostly monosyllabic and seldom dissyllabic words. They had not been previously used with these subjects. Each series contained ten words or ten objects. The same kind of precautions were taken as in the couplet sets to avoid phonetic aids and the juxtaposition of words which suggest each other. The apparatus employed in the couplet sets was used. The objects in the object series were shown through the aperture. Visual images were required in the noun and in the verb series. The noun and the object series were exposed at the rate of one word every 2 secs. (or 20 secs. for the series) for M, S, and Hu, and one every 3 secs. (or 30 secs. for the series) for B, Ho, and Mo. Only one exposure of the series was given. At its completion the subject at once wrote as many of the words or objects as he could recall. Two days later at the same hour he was asked to write without further stimulus as many words of each series as he could recall, classifying them according to their type of series.

The verbs were similar to the verbs of the couplet series. There was a tendency in the verb series among most of the subjects to make a more or less connected story of the verbs and thus some subjects could retain all ten words for two days. This was an element not present in the couplet verb series, according to the subjects, nor in any other series, and the subjects were, therefore, directed to eliminate it by imaging each action in a different place and connected with different persons. The effort was nearly successful, some of the subjects connecting two or three verbs, and others none. The movements employed ten objects which were uncovered and covered by the subject as in the C set. The exposure for the verbs and movements was 5 secs. for each word, or 50 secs. for the series. The tests were the same as in the series of ten nouns and ten objects, but in a number of cases (to be specified in the table) it seemed best to shorten the interval for deferred recall to one day.

The series were always given in pairs—a noun and an object series, or a verb and a movement series forming a pair. Only one pair was given per day and no other series of any kind were given on that day. Usually several days intervened between the II. test of one pair and the learning of the next, but in a little less than half of the cases a new pair was learned on the same day shortly after the II. test of the preceding pair.

The noun-object pairs and the verb-movement pairs were not given in any definite order with reference to each other.

The figures in the following table indicate the number of words out of ten which the subject correctly recalled and placed in their proper columns. Immediate recall is also given.

TABLE VII.

¹ One day.

The results of the D set strongly confirm the results of the A, B, and C sets. Table VII. shows that after from one to two days' interval four subjects recall objects better than nouns and movements better than verbs. One subject, M., shows no preference.

CONCLUSIONS.

We are now in a position to answer specifically the problem of this investigation. The results show: (1) that those five subjects who recall objects better than nouns (involving images) when each occurs alone, also recall objects better than nouns when each is recalled by means of an unfamiliar verbal symbol with which it has been coupled; (2) that the same is true of verbs and movements; (3) that these facts also receive confirmation on the negative side, viz.: the one subject who does not recall objects and movements better than nouns and verbs (involving images) when they are used alone, also does not recall them better when they are recalled by means of foreign symbols with which they have been coupled.

MINOR QUESTIONS.

The problem proposed at the outset of the investigation having been answered, two minor questions remain: (1) as to images, (2) indirect associations.

1. All the subjects were good visualizers. The images became clear usually during the first of the three presentations, i.e., in 1-3 secs., and persisted until the next couplet appeared. In the second and third presentations the same images recurred, rarely a new one appeared.

An interesting side light is thrown on M.'s memory by his work in another experiment in which he was a subject. This experiment required that the subject look at an object for 10 secs. and then after the disappearance of its after-image manipulate the memory image. M. showed unusually persistent after-images. The memory images which followed were unusually clear in details and also persistent. They were moreover retained for weeks, as was shown by his surprising ability to recall the details of an image long past, and separated from the present one by many subsequent images. His memory was capacious rather than selective. His eyesight was tested and found to be normal for the range of the apparatus. Possibly his age (55 yrs.) is significant, although one of the two subjects who showed the greatest preference for objects and movements, Mo., was only six yrs. younger. The ages of the other subjects were S. 36 yrs., Hu. 23 yrs., B. 25 yrs., Ho. 27 yrs.

That some if not all of the subjects did not have objective images in many of the noun and verb couplets if they were left to their own initiative to obtain them is evident from the image records in the A set, in which the presence of the objective images was optional but the record obligatory. The same subject might have in one noun or verb series no visual images and in another he might have one for every couplet of the series. After the completion of the A set, the effect of the presence of the objective images in series of 10 nouns alone, or 10 objects alone after two days' interval, was tested. This was merely a repetition of similar work by Kirkpatrick after three days' interval, and yielded similar results. As a matter of fact some of the subjects were unable wholly to exclude the objective images, but were compelled to admit and then suppress them as far as possible, so that it is really a question of degree of prominence and duration of the images.

The presence of the objective images having been shown to be an aid in the case of series of nouns, the subjects were henceforth requested to obtain them in the noun and verb series of the B and C sets, and the image records show that they were entirely successful in doing so.

2. The total number of couplets in any one or in several sets may be divided into two classes: (1) Those in which indirect associations did not occur in the learning, and (2) those in which they did occur. For reasons already named we may call the first pure material and the second mixed. We can then ascertain in each the proportion of correctly recalled couplets after one, two, nine and sixteen days' interval, and thus see the importance of indirect associations as a factor in recall. This is what has been done in the following table.

The figures give the number of couplets correctly or incorrectly recalled out of 64. In the case of the interval of one day the figures are a tabulation of the III. test (twenty-one hours) of the C set, which contained 16 series of 4 couplets each. The figures for the intervals of two, nine and sixteen days are a tabulation of the B set, which also contained 16 series of 4 couplets each. C denotes correct, I incorrect.

TABLE VIII.

SHOWING GREATER PERMANENCE OF COUPLETS IN WHICH INDIRECT ASSOCIATIONS OCCURRED.

We see from the table that the likelihood of recalling couplets in which indirect associations did not occur in learning is 63 per cent. after one day, and that there is a diminution of 44 per cent. in the next fifteen days. The fall is greatest during the second day. On the other hand, the likelihood of recalling couplets in which indirect associations did occur is 82 per cent. after one day, and there is a diminution of only 18 per cent. during the next fifteen days. The fading is also much more gradual.

It is evident, then, that in all investigations dealing with language material the factor of indirect associations—a largely accidental factor affecting varying amounts of the total material (in these six subjects from 3 per cent. to 23 per cent.) is by far the most influential of all the factors, and any investigations which have heretofore failed to isolate it are not conclusive as to other factors.

The practical value of the foregoing investigation will be found in its bearing upon the acquisition of language. While it is by no means confined to the acquisition of the vocabulary of a foreign language, but is also applicable to the acquisition of the vocabulary of the native language, it is the former bearing which is perhaps more obvious. If it is important that one become able as speedily as possible to grasp the meaning of foreign words, the results of the foregoing investigation indicate the method one should adopt.

FOOTNOTES.

1 Kirkpatrick, E.A.: PSYCHOLOGICAL, REVIEW, 1894, Vol. I., p. 602.

2 Calkins, M.W.: PSYCHOLOGICAL, REVIEW, 1898, Vol. V., p. 451.

MUTUAL INHIBITION OF MEMORY IMAGES.

BY FREDERICK MEAKIN.

The results here presented are the record of a preliminary inquiry rather than a definitive statement of principles.

The effort to construct a satisfactory theory of inhibition has given rise, in recent years, to a good deal of discussion. Ever since it was discovered that the reflexes of the spinal cord are normally modified or restrained by the activity of the brain and Setschenow (1863) attempted to prove the existence of localized inhibition centers, the need of such a theory has been felt. The discussion, however, has been mainly physiological, and we cannot undertake to follow it here. The psychologist may not be indifferent, of course, to any comprehensive theory of nervous action. He works, indeed, under a general presumption which takes for granted a constant and definite relation between psychical and cerebral processes. But pending the settlement of the physiological question he may still continue with the study of facts to which general expression may be given under some theory of psychical inhibition not inconsistent with the findings of the physiologist.

A question of definition, however, confronts us here. Can we, it may be asked, speak of psychical inhibition at all? Does one conscious state exercise pressure on another, either to induce it, or to expel it from the field? 'Force' and 'pressure,' however pertinent to physical inquiries, are surely out of place in an investigation of the relations between the phenomena of mind. Plainly a distinction has to be made if we are to carry over the concept of inhibition from the domain of nervous activity to the conscious domain. Inhibition cannot, it should seem, have the same sense in both. We find, accordingly, that Baldwin, who defines nervous inhibition as 'interference with the normal result of a nervous excitement by an opposing force,' says of mental inhibition that it 'exists in so far as the occurrence of a mental process prevents the simultaneous occurrence of other mental processes which might otherwise take place.'1

Even here, it may be said, there is in the term 'prevents' an implication of the direct exercise of force. But if we abstract from any such implication, and conceive of such force as the term inhibition seems to connote, as restricted to the associated neural or physiological processes, no unwarranted assumptions need be imported by the term into the facts, and the definition may, perhaps, suffice.

Some careful work has been done in the general field of psychical inhibition. In fact, the question of inhibition could hardly be avoided in any inquiry concerning attention or volition. A. Binet2 reports certain experiments in regard to the rivalry of conscious states. But the states considered were more properly those of attention and volition than of mere ideation. And the same author reports later3 examples of antagonism between images and sensations, showing how the latter may be affected, and in some respects inhibited, by the former. But this is inhibition of sensations rather than of ideas. Again, Binet, in collaboration with Victor Henri,4 reports certain inhibitory effects produced in the phenomena of speech. But here again the material studied was volitional. More recently, G. Heymans5 has made elaborate investigation of a certain phase of 'psychische Hemmung,' and showed how the threshold of perception may be raised, for the various special senses, by the interaction of rival sensations, justly contending that this shifting of the threshold measures the degree in which the original sensation is inhibited by its rival. But the field of inquiry was in that case strictly sensational. We find also a discussion by Robert Saxinger,6 'Ueber den Einfluss der Gefühle auf die Vorstellungsbewegung.' But the treatment there, aside from the fact that it deals with the emotions, is theoretical rather than experimental.

In short, it appears that though much has been said and done upon the general subject of psychical inhibition, experimental inquiry into the inhibitory effect of one idea upon another—abstraction made, as far as possible, of all volitional influence—virtually introduces us to a new phase of the subject.

The term 'idea,' it should be noted, is here used in its broadest sense, and includes the memory image. In fact, the memory image and its behavior in relation to another memory image formed the material of the first part of the research, which alone is reported here. Apparatus and method were both very simple.

The ideas to be compared were suggested by geometrical figures cut out of pasteboard and hung, 25 cm. apart, upon a small black stand placed on a table in front of the observer, who sat at a distance of four feet from the stand. The diagrams and descriptions which follow will show the character of these figures.

Before the figures were placed in position, the subject was asked to close his eyes. The figures being placed, a few seconds' warning was given, and at the word 'look' the subject opened his eyes and looked at the objects, closing his eyes again at the word 'close.' The time of exposure was five seconds. This time was divided as equally as possible between the two figures, which were simultaneously exposed, the observer glancing freely from one to the other as in the common observation on which our ideas of objects are founded. At the end of the exposure the subject sat with closed eyes and reported the several appearances and disappearances of the ideas or mental images of the objects just presented. The conditions required of him were that he should await passively the entry of the rival claimants on his attention, favoring neither and inhibiting neither; that is to say, he was to remit all volitional activity, save so far as was necessary to restrict his attention to the general field upon which the ideated objects might appear, and to note what occurred on the field. The period of introspection, which followed immediately the disappearance of such retinal images as remained, after the closing of the eyes to the external objects, lasted sixty seconds. The reports, like the signals, were given in a just audible tone. They were in such terms as 'right—left,' 'small—large,' 'circle—star,' terms the simplest that could be found, or such as seemed, in any given case, most naturally or automatically associated with the object, and therefore least likely to disturb the course of the observation. And each report was noted down by the experimenter at the instant it was given, with the time of each phase, in seconds, as indicated by a stop-watch under the experimenter's eye.

It will be remarked that the attitude required of the observer was one which is not commonly taken. And it may be objected that the results of an attitude so unusual towards objects so ghostly and attenuated must be too delicate, or too complex, or influenced by too many alien suggestions, to be plumply set down in arabic numerals. The subjects, in fact, did at first find the attitude not easy to assume. A visual object may hold the attention by controlling the reflexes of the eye. But an ideational object has ordinarily no sure command of the conscious field save under the influence of a volitional idea or some strongly toned affectional state. But with a little practice the difficulty seemed to disappear. The subject became surer of his material, and the mental object gradually acquired the same sort of individuality as the visual object, though the impression it made might be less intense.

After a few preliminary experiments, figures were devised for the purpose of testing the effect of mere difference in the complexity of outline. That is to say, the members of every pair of objects were of the same uniform color-tone (Bradley's neutral gray No. 2), presented the same extent of surface (approximately 42 sq. cm.), were exposed simultaneously for the same length of time (5 seconds), and were in contour usually of like general character save that the bounding line in the one was more interrupted and complex than in the other.

In another series the variant was the extent of surface exposed, the color-tone (neutral gray), outline, and other conditions being the same for both members of each pair. The smaller figures were of the same area as those of the preceding series; in the larger figures this area was doubled. Only one member of each pair is represented in the diagrams of this and the next series.

In a third series brightness was the variant, one member of each pair being white and the other gray (Bradley's cool gray No. 2). All other conditions were for both figures the same.

In still another series strips of granite-gray cardboard half a centimeter wide were cut out and pasted on black cards, some in straight and some in broken lines, but all of the same total length (10 cm.). These were exposed under the same general conditions as those which have already been described, and were intended to show the relative effects of the two sorts of lines.

TABLE I.

The Arabic numerals at the head of the columns refer, in every table, to the corresponding numerals designating the objects in the diagram accompanying the table.

L: left-hand object. R: right-hand object.

The Roman numerals (I to XI) indicate the different subjects. The same subjects appear in all the experiments, and under the same designation. Two of the subjects, IV and VIII, are women.

The numbers under L and R denote the number of seconds during which the left-hand image and the right-hand image, respectively, were present in the period of introspection (60 seconds).

General average: L, 30.8 sec.; R, 31.9 sec.

Fig. 1.

Series No. 1.—For the purpose of obtaining something that might serve as a standard of comparison, a series of observations was made in which the members of every pair were exact duplicates of each other, and were presented under exactly the same conditions, spatial position of course excepted. The records of these observations are for convenience placed first as Table I.

In treating the facts recorded in the accompanying tables as phenomena of inhibition no assumption is implied, it may be well to repeat, that the ideational images are forces struggling with each other for mastery. Nor is it implied, on the other hand, that they are wholly unconditioned facts, unrelated to any phenomena in which we are accustomed to see the expression of energy. Inhibition is meaningless save as an implication of power lodged somewhere. The implication is that these changes are conditioned and systematic, and that among the conditions of our ideas, if not among the ideas themselves, power is exerted and an inferior yields to a superior force. Such force, in accordance with our general presupposition, must be neural or cerebral. Even mental inhibition, therefore, must ultimately refer to the physical conditions of the psychical fact. But the reference, to have any scientific value, must be made as definite as the case will allow. We must at least show what are the conditions under which a state of consciousness which might otherwise occur does not occur. When such conditions are pointed out, and then only, we have a case of what has been called psychical inhibition; and we are justified in calling it inhibition because these are precisely the conditions under which physiological inhibition may properly be inferred. And, we may add, in order that the conditions may be intelligibly stated and compared they must be referable to some objective, cognizable fact. Here the accessible facts, the experiential data, to which the psychical changes observed and the cerebral changes assumed may both be referred, are visual objects, namely, the figures already described.